How can SELinux be set to permissive mode upon booting?

Setting SELinux to permissive mode upon booting can be achieved by modifying the kernel boot parameters. When you add the argument "enforcing=0" in the kernel parameters, it instructs the kernel to start SELinux in permissive mode during the boot process. This means that, while SELinux will be active, it will only log the actions that would have been denied instead of enforcing them, allowing you to see the potential denials without enforcing policy restrictions.

In contrast, while setting "SELINUX=permissive" in the SELinux configuration file does change the mode to permissive, it will only take effect after the system has already booted, requiring a restart of the SELinux service or a reboot to fully activate. Disabling the SELinux service entirely is not a recommended practice, as it can expose the system to security risks by removing the protections that SELinux provides. The setenforce command allows for temporary changes in the SELinux mode but does not provide a persistent setting upon reboot, as it applies only to the current session. Therefore, modifying the kernel arguments is the most effective way to ensure SELinux boots in permissive mode.